This invention relates to a spring brake actuator wherein a release bolt moves a caging member within the emergency chamber an amplified amount for each unit of movement of the release bolt outwardly of the brake actuator chamber.
Spring brake actuators include an emergency or parking side enclosing a strong power spring. The power spring selectively actuates a push rod in the service side of the brake actuator. The service side is normally operated by air pressure to move the push rod and set the brake. Under certain conditions, the emergency side may actuate the push rod. One of those conditions is a failure in the brake air system. Upon a failure of the air system, the power spring expands and moves the push rod. The push rod sets the brake, preventing movement of the vehicle.
Under such conditions, a driver typically must cage the power spring to allow the vehicle to be moved. In the majority of the prior art brake actuators, a release bolt is associated with the spring brake actuator housing. The release bolt is moved into the emergency chamber and pulls a threaded plate outwardly to capture or cage the power spring. In addition to emergency situations, caging is utilized for shipment, repair, or other situations where the actuator is out of use for a period of time. Prior art release bolts have typically needed to extend outwardly of the housing a significant distance before beginning to cage the power spring.
In addition, so-called integral release bolts have been received in the brake actuator housing. Integral release bolts typically move outwardly of the housing a significant distance as they cage the power spring.
With both of these prior art caging systems, the release bolt must extend outwardly of the brake actuator a significant distance during caging of the power spring. Brake actuators are typically mounted beneath vehicles, and are often in a crowded space. The mounting of the brake actuator relative to other structure on the vehicle is such that there may not be enough room for the release bolt to extend outwardly of the brake actuator the necessary distance.